Method of finishing spline shafts



July 21, 1931.

c. L. LEE ET AL 1,815,626

METHOD OF FINISHING SPLINE SHAFI'S Filed Nov. 28, 192'! 2 Sheets-Sheet 1 gin Danton:

C/aua E ffr/z y (LC/fa r/es, L1 1: e2

attomqq July 211, 1931. c. 1.. LEE ETAL 1,315,625

METHOD OF FINISHING SPLINE SHAFTS I Filed Nov. 28. 1,92 2'Sheets-Sheet 2 Qwumtow Patented July 21, 1931 QHARLES- L- LEE r AY QR H O. AND: LAUDE SIERLINQ, F. ETR IT MI HI- e AssIGNoRs mo. GENERAL IYLQTQRS, efinance CORPORATION, F DEF-301T, momma. QBB BA I N or DELAWARE.-

METHOD OF FINISHING SPLINE- smir'rs Application filed November 28, 1927'. Serial No. 236,218.

This invention relates to splineshafts. for carrying the slidable gears of anautomobile variable speed transmission and for similar purposes; it also relates to the process of lfinishing splinefshafts. v p

' In making spline shafts for use. in the tomary to hob orothervvise machinethe lands and grooves in a blank of machinable steel,

7 loftherea'fter to heat-treat and-hardenthe machined shaft, andsubsequently grind the longitudinal surfaces at the bottoms of the grooves and the sides ofthe lands. In the heat treating process, more or less distortion isapt to occur, consequently the shaft is originally machined slightly over-slze a llld e the excess metal removed by grinding. irregularities that may be. developed by the heat treating and hardening. process are smoothed out by the act of grinding." If; the

' shaft isv greatly distorted it'must be strai 'ghtened, as in a bulldozing press, or scrapped. We have ascertained that a superior spline shaft can be made by first machining the blank, leaving a slight excess of metalon the sides of 'the lands and at the bottoms of the grooves, then heat treating and hardening,

and subsequently 'cold swa'ging the shaft from'end to end'by pressureiprogressively applied simultaneously between all-of: the lands,beginning the swaging. operation at one end ofrthe shaft and: progressing to the other by small advances.

We have found that shaftsbodily distorted and lands warped during heat treating. may

be straightened bodily and progressively swaged' at the same time, as described, and the surface condensed and-polished Where the slidable gears rub upon the: shaft,-thus pro- Fig. 2 is a front elevation of the machine shown in Fig. 1

Fig. isa front elevation, partly in sec- The shaft and head may the pulley 14a to a prime mover.

ducing superiorsmooth and hard bearing tion, the. section. having been taken on the line 33-0f Fig; 1.

- Fig. 4:lS anenlargedvievv of. an individual svvaging tool suoh as isusedin this machine, together with a' hammenblock and. spacing ,shim assembled with it,

transmissions of; motor vehicles it is cusi Fig. 5' is an elevation of a conventional spline shaftofthe kind used in automobile transmissions. r 1

Fig.6 is an .end elevation ofthe spline shaft shownin Fig. 5, and i Fig.7 is a cross section ofa fragment of a spline shaft exaggerated in size,after have n; wa e -1 Referringto the drawings, 10 indicates the baseof a swagingmachine. Bolted to this baseis abearing standard or shaft hangerll hav n ao ns and a c ng v n a bearing opening alined with the, bearing. in the hanger 111 andalsoenlargedhollowcasing portion 13 which housesthe swaging tools and. operating mechanism therefor. Extending through the bearing openings in the members 11- and 12 is a hollow shaft 14 which is. located longitudinally by pulley 14,04 fixed,

to it by collar 15 arranged,to.engage the outer face of-the hanger 11 and a hub 16 formed on a rotary swaginghead 17; whichiiskeyed and securely: fixed to the shaftl l at its front end.

A. detachable face plate 18 is secured 1 against a-plane, annular surface formed on the front of casing portion 13. This face plate is preferablysecured by strong bolts 19; The faceplate has a tapering opening 181: at; the center and has a, centrally perforated, svvage guide 20, extending into the hollow oof the rotary swaging head. Radial,

parallel sided guideways 20a are formed in the cylindrical guide 20, said guidewaysextending from t'he'hollow centerthrough to the exterior surface. In the machine shown there are SlX of such radial guide a-ys arrangedin three pairs, each pair being centrally traversed by the same diametrical plane. In each guideway a svvage tool 21 and a hammer block 22 are slidably fitted.

Betweenthe swagetool 21 and the. hammer block22 a shim or adjusting plate 23 may e rotated belting.

' of the hammer blocks. is a set of hard rollers 24 properly spaced by a cage 25. The arrangement of swages and operating mechanism causes each swage to be exactly opposed during its working stroke by another swage on the other side of the axis of the shaft 14.

The front sides of the radial guideways in swage guide 20 are open from the zone 26 inward toward the central opening. A door 27, hinged on pintle 28, is provided with a flange 29 adapted to fit against the front of an annular raised surface 30 provided on face plate 18. Into the enlarged and tapering front portion of the opening 18a in said face plate the door projects. Said door carries on its inner face a hard steel plate 81, the inner surface of which serves to close the open side of the guideways and complete the guide in which the swaging tools and hammer blocks are slidably confined. When the door is closed it may be locked by the locking pin 32. The

center of the door is open, as shown, to admit the shaft to be swaged when the door is locked. When the door is open the swage blocks may be drawn out through opening 18a and the hammer blocks and shims may then be dropped to the center by gravity or pushed toward the center so that they also may be readily removed.

The working end of each sawging tool 21 is inclined slightly away from the axis of shaft 14 and head 17 from rear to front in order that it may operate upon the shaft subjected to it gradually. As the end of the shaft is inserted into the opening between the swages the front of each swage which is most distant radially from the axis of the shaft, first acts and produces a minute reduction. As the shaft is pushed further inward the portions of the working face of the swage that are nearer to the center of the shaft or the orifice into which it is inserted increase the reduction, the final reduction being made by the inner or rearward edge of the working face. The inclined faces of the swages are indicated in Fig. 1 and also at 34 in Fig. 4. The edges 35 of each swage are sharp, not rounded. When the swaging tools are near the end of their working strokes they squeeze the lands between their inclined faces. The sharp corners or edges at the end of the swages tend to form small shoulders or burrs at 41 by swaging and scraping action.

As shown in Figs. 5,- 6, and 7, the shaft is machined with bearing surfaces 38 at the bottom of the grooves, these surfaces being slightly elevated radially leaving, small grooves 39 between the surface 38 and the sides of the lands 40. In the swaging operations the ends of the swaging tools press simultaneously upon the several surfaces 38 and bring them after successive applications of pressure to the desired diameter and polish. The grooves 39 provide space for the metal to flow laterally, and also to receive any metal that may be scraped from the sides of the lands without obstructing the internal angles of the grooves. Fig. 7 indicates on an enlarged scale the spread of the metal toward the grooves 39 after the shaft has been swaged as indicated at 38a and the slight burrs or shoulders 41 formed on the sides of the lands. The metal of the lands being squeezed between opposed swaging dies will be straightened if distorted and metal may fiow radially to the slight extent necessary to produce the required result. The finished product is a shaft having highly burnished" bearing surfaces on a hard condensed skin produced by heavy pressure applied to the shaft at successive zones throughout its length.

The swaging machine illustrated is of a well known type specifically adapted by the shape of the swaging tools to practice the process of this invention. The blank spline shaft may be inserted through. the opening in the door 27 as shown at the right of Fig. 1 and advanced gradually by hand or otherwise between the swaging tools, while the pulley 14a is rotating and communicating rotary motion to the head 17. The hard rollers 24 journaled in the cage 25 are caused to roll by contact with the inner periphery of the head thus causing the cage to revolve with the axes of the rollers moving around the blank at a slower rate of speed than and in the same direction as the head. When the rollers contact with the hammer blocks 22 they press the swages radially inward leaving them free to be moved radially outward. after the rollers have passed them until the next rollers engage the hammer blocks.

' After completion of the swaging operation no further finishing act is applied except to grind the outer faces of the lands concentric with the axis of the shaft.

By the described process warped shafts are straightened and given a hard smooth accurate bearing surface in the same operation. It is therefore unnecessary to straighten badly warped shafts in a press before finishing, nor is it necessary to provide so much excess of metal as would be required to true badly warped shafts by abrading.

We claim:

1. The process of making spline shafts which consists in first machining a blank of steel to form longitudinal lands and grooves, t hen heat treating and hardening the shaft and then progressively cold swaging the bearing surfaces from end to end.

2. The process of making spline shafts which consists in machining a blank of steel so as to form an over-size shaft having grooves and lands, each groove having a bearing surface at its bottom separated from the lands by a longitudinal groove on each side, heat treating and hardening the blank, then progressively cold swaging the hardened blank from end to end between the lands, thereby bringing the shaft to final size, and straightening it.

In testimony whereof we aflix our signatures.

CHARLES L. LEE. CLAUDE H. STERLING. 

